Heslop D D, Bi Y, Baig A A, Otsuka M, Higuchi W I
Department of Pharmaceutics and Pharmaceutical Chemistry, 213 A Skaggs Hall, University of Utah, Salt Lake City, 84112, USA.
J Colloid Interface Sci. 2005 Sep 1;289(1):14-25. doi: 10.1016/j.jcis.2004.12.050.
Using solution strontium and pH as independent variables, the metastable equilibrium solubility (MES) behavior of two carbonated apatite (CAP) samples has been examined, a high-crystallinity CAP (properties expected to be similar to dental enamel) and a low-crystallinity CAP (properties expected to be similar to bone mineral). CAP samples were prepared by precipitation/digestion: (CAP A: high-crystallinity, 1.3 wt% CO3, synthesized at 85 degrees C; CAP B: low-crystallinity, 6.4 wt% CO3, synthesized at 50 degrees C). Baseline MES distributions were determined in a series of 0.1 M acetate buffers containing only calcium and phosphate (no strontium) over a broad range of solution conditions. To assess the influence of strontium, MES profiles were determined in a similar fashion with 20, 40, 60, and 80% of the solution calcium being replaced on an equal molar basis by solution strontium. To determine the correct function governing CAP dissolution, ion activity products (IAPs) were calculated from the compositions of buffer solutions based on the hydroxyapatite template (Ca(10-n)Sr(n)(PO4)6(OH)2 (n = 0-10)) and the calcium/hydroxide deficient hydroxyapatite template (Ca(9-n)Sr(n)(HPO4)(PO4)5OH (n = 0-9)).
(a) for CAP A, at high solution strontium/calcium ratios, the MES profiles were essentially superimposable when the solution IAPs were calculated using the stoichiometry of Ca6Sr4(PO4)6(OH)2 and for CAP B by a stoichiometry of Ca7Sr2(HPO4)(PO4)5OH; (b) for CAP A, at low strontium/calcium ratios, the stoichiometry yielding MES data superpositioning was found to be that of hydroxyapatite and for CAP B, that of calcium/hydroxide deficient hydroxyapatite. When other stoichiometries were assumed, good superpositioning of the data was not possible.
以溶液锶和pH值作为自变量，研究了两种碳酸化磷灰石（CAP）样品的亚稳平衡溶解度（MES）行为，一种是高结晶度的CAP（性质预计与牙釉质相似），另一种是低结晶度的CAP（性质预计与骨矿物质相似）。通过沉淀/陈化法制备CAP样品：（CAP A：高结晶度，1.3 wt% CO3，在85℃合成；CAP B：低结晶度，6.4 wt% CO3，在50℃合成）。在一系列仅含钙和磷酸盐（不含锶）的0.1 M乙酸盐缓冲液中，于广泛的溶液条件下测定基线MES分布。为评估锶的影响，以类似方式测定MES曲线，其中溶液中20%、40%、60%和80%的钙被等摩尔的溶液锶取代。为确定控制CAP溶解的正确函数，根据羟基磷灰石模板（Ca(10 - n)Sr(n)(PO4)6(OH)2 ，n = 0 - 10）和缺钙/氢氧根的羟基磷灰石模板（Ca(9 - n)Sr(n)(HPO4)(PO4)5OH ，n = 0 - 9），从缓冲溶液的组成计算离子活度积（IAPs）。
（a）对于CAP A，在高溶液锶/钙比时，当使用Ca6Sr4(PO4)6(OH)2的化学计量计算溶液IAPs时，MES曲线基本可叠加，对于CAP B，使用Ca7Sr2(HPO4)(PO4)5OH的化学计量计算时，MES曲线基本可叠加；（b）对于CAP A，在低锶/钙比时，发现产生MES数据叠加的化学计量是羟基磷灰石的化学计量，对于CAP B，是缺钙/氢氧根的羟基磷灰石的化学计量。当假设其他化学计量时，数据无法实现良好叠加。
